The ability to store and preserve red blood cells (RBCs) for later re-infusion into patients is a technological development that has helped advance modern surgical practices. This preservation is scientifically challenging and the steps to achieving longer storage duration and higher quality re-infused red blood cells have been incremental. As soon as RBCs are collected from a donor, they begin to die as they coagulate, starve, lose adenosine triphosphate (ATP), 2,3-Bisphosphoglycerate (2,3-DPG), membrane surface area and integrity, and hemoglobin (Hb).
Initially, storage compositions were designed to be acidic to prevent the caramelization of the glucose during heat sterilization performed in the final production step. In the 1950s, adenine was discovered to be useful a useful additive to replace the adenine lost by deamination. Thereafter, in the 1970s it became desirable to remove plasma from collected whole blood for platelets and to manufacture of plasma derivatives. However, this has led to a reduction in the percent recovery of the resulting “packed RBC.”
To overcome this deficiency, compositions known in the art as additive solutions have been developed to restore volume, nutrients, and other useful RBC stabilizers. Additive solution compositions for the preservation of RBCs after their separation from whole blood are intended to be tailored specifically to the needs of RBCs, and the development of certain additive solutions has extended RBC storage to about 6 weeks. However, RBCs stored in these solutions undergo steady deterioration. It has been observed that during continued refrigerated storage, glucose is consumed at a decreasing rate, as the concentration of metabolic waste, i.e. lactic acid and hydrogen ions, increases. Such a decrease in the rate of glucose metabolism leads to depletion of adenosine triphosphate ATP, which directly correlates to the recovery of RBCs when the cells are returned to the circulation. Additive solutions such as Adsol® (AS-1), Nutricel® (AS-3), Optisol® (AS-5), and ErythroSol® have been designed to extend the storage of RBCs at 1-6° C.
Almost all of the whole blood collected now is made into components, and the RBC fraction is stored as packed RBCs. For blood drawn into the additive solution systems, RBCs are packed by centrifugation, plasma is removed so that RBCs make up 80% of the volume, and then 100 ml of an additive solution is sterilely added. The resulting suspensions have a RBC volume fraction of approximately 55%. RBCs stored in conventional FDA-approved additive solutions can be stored for only 6 weeks with an acceptable 24-hour in vivo recovery.
To increase the time of acceptable in vivo recovery of RBCs re-infused into patients after a storage period, attempts have been made to improve the additive solutions and/or storage processes. For example, U.S. Pat. No. 8,709,707 and U.S. Pat. Pub. No. 2005/0233302 both to Hess et al., the subject matter of each of which is herein incorporated by reference in its entirety, describes compositions and methods for the storage of RBCs.
Increased duration of RBC storage remains an important consideration during periods when demand is high but intermittent, such as during wartime, natural disasters and for geographical regions that require transfusable blood but only on an inconsistent and sporadic basis. In fact, given the current level of reported waste due to expiration of the safe storage period prior to realization of a demand in general, increasing the duration of time that RBCs may be safely stored is an ongoing concern.
Furthermore, although considered generally safe, blood transfusions have noteworthy risks associated with them, particularly when the blood has been stored for several weeks prior to transfusion. Although the current FDA regulations allow blood storage for up to 42 days in approved solutions at 4° C., transfusion of RBCs stored for over 21 days have led to negative clinical outcomes for blood recipients.
For example, human studies have shown that transfusion of older RBC units loads to increased risk of mortality and morbidity in critically ill patients with acute lung injury, decreased peripheral tissue oxygenation in pediatric and elderly patients, decreased cerebral oxygenation in patients with traumatic brain injury, and multiple organ failure as reported in Cho et al., The road to advanced glycation end products: a mechanistic perspective, Curr. Med. Chem. (2007) Vol. 14, pp. 1653-1671 and Vasan et al., Therapeutic potential of breakers of advanced glycation end product-protein crosslinks, Arch. Biochem. Biophys. (2003) Vol. 419, pp. 89-96.
The loss of RBC integrity during storage has been ascribed to a number of causes, including formation of advanced glycation end-products (AGEs)—a heterogeneous mixture of compounds formed by chemical reactions between specific sugars and proteins.
During the storage of collected RBC units, AGEs are thought to accumulate over time, due to the high amounts of glucose present in currently approved storage buffers. In fact, human RBCs stored in a FDA approved storage solution (adenine, dextrose, sodium chloride, and mannitol) showed a three-fold increase in the AGE levels compared to fresh blood.
AGEs are considered toxic to cells and may contribute to complications after RBC transfusion. Additionally, these accumulating AGEs may be responsible for increasing the immunogenicity of RBCs, resulting in decreased survival of RBCs.
Thus, there remains a need for improved RBC storage that results in longer storage duration, better recovery percentage, and improved physiological functioning of the transfused RBC. Consequently, there remains a need for improved RBC storage solutions and processes of manufacture thereof. There is also a continuing need for additive solutions which allow the RBC suspension to which the solution is added to be directly infused into humans, and which permit an acceptable post-infusion recoverability of viable RBCs possessing enhanced physiological functioning capabilities and lower rates of clearance from the infused patient's circulation.
The inventors of the present invention have found that AGE crosslink breakers can be used as a component of an additive solution that allows more effective recovery of RBCs during storage by retarding and reversing AGE formation on blood cells.
As described herein, AGEs are formed on RBCs during storage with glucose and lead to immunogenicity. The inventors of the present invention set out to determine a method to better preserve blood products by inhibiting this degradation pathway of RBCs.